The present invention relates to a spherical- or dome-shaped bulb fluorescent lamp.
In addition to incandescent lamps, fluorescent lamps have been widely used for interior lighting, but they are in general in the form of a tube, a ring and a flat panel so that even though their efficiency is considerably higher than that of the incandescent lamps they have a relatively large light emitting surface. That is, they are a low luminous light source so that they are not adapted for spot lighting or so-called accentuation lighting for emphasizing or exaggerating the contrast between the illuminated and dark areas of an object. On the other hand, the incandescent lamps are compact in size and have a high luminous efficiency so that they are best adapted for the so-called accentuation lighting, but their efficiency is about 15 lm/w which is considerably lower than the efficiency of 60 to 80 lm/w of the fluorescent lamps.
Because of the above disadvantages of the fluorescent lamps over the incandescent lamps as well as the energy saving problems there has been a growing demand for a fluorescent lamp which is compact in size yet retains its high lamp efficiency and may be used instead of the incandescent lamps. Demands only for high luminousity and efficiency are satisfied by the conventional high pressure vapour discharge lamps such as high-pressure mercury lamps, metal halide lamps or the like, but these lamps have a common and fatal disadvantage in that instant re-starting is impossible so that they cannot replace the incandescent lamps and the fluorescent lamps which may be re-started at a lower voltage.